Laboratory diagnosis of respiratory diseases: PCR versus serology

Community-acquired pneumonia

Community-acquired pneumonia is not usually considered a high-priority problem by the public, although it is responsible for substantial mortality, with a third of patients dying within 1 year after being discharged from hospital for pneumoniae. Although up to 18% of patients with community-acquired pneumonia who were hospitalised (admitted to hospital and treated there) have at least one risk factor for immunosuppression worldwide, strong evidence on community-acquired pneumonia management in this population is scarce. Several features of clinical management for community-acquired pneumonia should be addressed to reduce mortality, morbidity, and complications related to community-acquired pneumonia in patients who are immunocompetent and patients who are immunocompromised. These features include rapid diagnosis, microbiological investigation, prevention and management of complications (eg, respiratory failure, sepsis, and multiorgan failure), empirical antibiotic therapy in accordance with patient's risk factors and local microbiological epidemiology, individualised antibiotic therapy according to microbiological data, appropriate outcomes for therapeutic switch from parenteral to oral antibiotics, discharge planning, and long-term follow-up. This Seminar offers an updated view on community-acquired pneumonia in adults, with suggestions for clinical and translational research.

Serum pooling for rapid expansion of anti-SARS-CoV-2 antibody testing capacity

Objectives

Examine possible pooling strategies designed to expand SARS-CoV-2 serological testing capacity.

Methods

Negative pools were assessed to determine optimal optical density (OD) cutoffs, followed by spiking weak or strong positive samples to assess initial assay performance. Samples were then randomly subjected to pool and individual testing approaches.

Results

Single positive specimens consistently converted pools of 5, 10, or 20 into positive outcomes. However, weaker IgG-positive samples failed to similarly convert pools of 50 to a positive result. In contrast, a stronger individual positive sample converted all pools tested into positive outcomes. Finally, examination of 150 samples configured into pools of 5, 10, 20 or 50 accurately predicted the presence of positive or negative specimens within each pool.

Conclusions

These results suggest that pooling strategies may allow expansion of serological testing capacity. While limitations exist, such strategies may aid in large-scale epidemiological screening or identification of optimal convalescent plasma donors.

Pooled analysis of nuclear acid sequence-based amplification for rapid diagnosis of Mycoplasma pneumoniae infection

Background

Mycoplasma pneumoniae(M pneumoniae) is a common human etiology of respiratory infections. Nuclear acid sequence‐based amplification (NASBA) shows good value for the detection of M pneumoniae that surpasses PCR. However, the optimal detection technology still remains to be identified. The purpose of this meta‐analysis was to systematically evaluate the overall accuracy of NASBA for diagnosing M pneumoniae infections.

Methods

The databases PubMed, Cochrane Library, Google Scholar, CNKI, Wang Fang, and Baidu Scholar were comprehensively searched from their initiation date to December 2017 for NASBA in the diagnosis of M pneumoniae infection. Meta‐DiSc 1.4 statistical software was used to evaluate the sensitivity (SEN), specificity (SPE), negative likelihood ratio (−LR), positive likelihood ratio (+LR), diagnostic odds ratio (DOR), and summary receiver operating characteristic (SROC). RevMan 5.2 statistical software was used for quality evaluation of the included articles. Publication bias was evaluated by funnel plot.

Results

Six articles with high quality, including 10 studies, were finally included in this meta‐analysis. The combined statistics results for the diagnosis of M pneumoniae infection by NASBA were 0.77 (SEN, 95% CI: 0.71 to 0.82); 0.98 (SPE, 95% CI: 0.98 to 0.99); 0.22 (‐LR, 95% CI: 0.13 to 0.39); 50.38 (+ LR, 95% CI: 21.85 to 116.17); 292.72 (DOR, 95% CI: 95.02 to 901.75); and 0.9875 (the area under the curve of SROC).

Conclusion

Nuclear acid sequence‐based amplification is a reliable technique to diagnose M pneumoniae infection. However, whether it can replace PCR and serology need to be further studied.

Laboratory Diagnosis of Pertussis

The introduction of vaccination in the 1950s significantly reduced the morbidity and mortality of pertussis. However, since the 1990s, a resurgence of pertussis has been observed in vaccinated populations, and a number of causes have been proposed for this phenomenon, including improved diagnostics, increased awareness, waning immunity, and pathogen adaptation. The resurgence of pertussis highlights the importance of standardized, sensitive, and specific laboratory diagnoses, the lack of which is responsible for the large differences in pertussis notifications between countries. Accurate laboratory diagnosis is also important for distinguishing between the several etiologic agents of pertussis-like diseases, which involve both viruses and bacteria. If pertussis is diagnosed in a timely manner, antibiotic treatment of the patient can mitigate the symptoms and prevent transmission. During an outbreak, timely diagnosis of pertussis allows prophylactic treatment of infants too young to be (fully) vaccinated, for whom pertussis is a severe, sometimes fatal disease. Finally, reliable diagnosis of pertussis is required to reveal trends in the (age-specific) disease incidence, which may point to changes in vaccine efficacy, waning immunity, and the emergence of vaccine-adapted strains. Here we review current approaches to the diagnosis of pertussis and discuss their limitations and strengths. In particular, we emphasize that the optimal diagnostic procedure depends on the stage of the disease, the age of the patient, and the vaccination status of the patient.